What kind of worm is white and flat and comes out of a dog's butt?

I believe it's called a tape worm. You need to get the dog to a vet. They will treat him for worms and probably give you something to give to the dog at home. It is possible for animals to die of worms if not treated.

yes its a tapeworm, you can treat it with the wormers you find at your local supermarket just make sure you adjust the dose for the weight of the dog ..the dosage isn't universal

I do believe that would be a tapeworm (tapeworm segments to be exact). In any case, you should bring the dog to a veterinarian. There the dog can be tested for any other intestinal worms it may have that cannot be physically seen, and it can be treated for any and all worms with a quality dewormer on a specific schedule over a period of time. I have never heard of dewormers being available at the local supermarket, but even if they are there you shouldn't trust them.

It is a tapeworm ( segments of a tapeworm ) and it is caused by your pet eating a flea. If you find one in your dogs poo, take him to the vet (it is not expensive) my English bulldog had one and it only cost $22 for two pills and it took care of the problem.

Sound like tape worm.They can look like small pieces of rice or several inches long(nasty but the truth) Give your vet a call.Tell them what they look like.Somtimes vet will just give you a bottle of the medicine & you give it once & then again in 14 days.That cures them.You can waste alot of money from buying from stores where you might better get from vet first saves money in the long run.Its not expensive I got a bottle which did 15 cats & 5 dogs for around $15.Best Of Luck!!